Abstract <p>Surface inspection under large strains is a critical problem for both civil and mechanical engineering. Optical techniques can be used for its solution. Digital image correlation (DIC) is one of these promising optical techniques; it is used to measure displacement and strain fields without contact with a surface under study. Input parameters can directly affect the strain field calculation accuracy. The correlation method is a key factor in DIC calculation of a strain field, especially under large strains. In this work, three spatial and incremental methods are tested; their accuracy and applicability are estimated; their advantages and drawbacks are discussed. The results can be useful for the developments of software for non-destructive testing.</p>